The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
A gas-fired, warm air furnace that operates at two fixed gas flow rates is generally referred to as a two-stage furnace. Two stage furnaces are frequently selected by homeowners over single stage furnaces because they offer increased performance and comfort. However, in two stage furnaces, the furnace controller is only configured to control a two stage gas valve that is operable at a fixed high gas flow rate and a fixed low gas flow rate. Such two stage gas valves are not capable of providing for adjustable gas flow rates. In multistage furnaces, a furnace controller may be configured to request operation of a modulating gas valve at a particular operating capacity level or gas flow rate. The operating capacity level requested by such furnace controllers could range from full capacity operation of the gas valve to as low as 30 percent of full capacity operation. However, the gas flow rate settings for the above gas valves are typically set at the factory, and are not field adjustable. Accordingly, a need still exists for an improved variable flow gas valve and associated control for such gas valves.